1. Field
The present invention relates generally to systems and methods associated with automated storage libraries, and more particularly to systems and methods for maneuvering storage device handling mechanisms within automated storage libraries.
2. Description of Related Art
Magnetic tape cartridges have proven to be an efficient and effective medium for data storage in computer systems. Large computer systems may utilize numerous cartridges for data storage purposes as well as a plurality of tape drives for inputting and outputting data to and from storage cartridges in a timely manner. Typically, as the number of storage cartridges grows they are organized in automated storage libraries. Automated storage libraries including, e.g., magnetic tape cartridges, may improve access speed and reliability of data storage systems having large numbers of magnetic tape cartridges.
Automated storage libraries generally include a plurality of storage bins or slots for storing storage devices (e.g., magnetic, optical, etc.), a robotic storage device picker mechanism (often referred to as a “gripper” or “hand”), and one or more media drives. The robotic picker may be controlled to select a specific storage device from the library and transfer the storage device between a storage slot and a media drive within seconds. The robotic picker typically includes a gripper or hand mechanism for handling the storage devices. For example, the robotic picker may position the gripper near a desired storage device and activate the gripper to engage or grip the storage device to remove the storage device from the storage bin. In other examples, a finger or hook may be used to engage and drag the storage device into or onto the transfer mechanism. The robotic arm may move the gripper and storage cartridge to a location to load the storage cartridge into a media drive, load port (for adding or removing tapes from the library), and the like.
Generally, storage device slots, media drives, access doors, and the like are arranged within a library housing to maximize the storage capacity for a given housing size. As a result, the picker mechanism generally moves in three dimensions when transferring storage devices between storage slots, media drives, and access doors. For example, the picker mechanism may move along a track in the x and y dimensions (on a plane parallel to the base), where the track includes one or more turns. The track may further rise in the vertical direction, the z-dimension, thereby allowing the picker mechanism three degrees of movement.
The density at which storage slots, media drives, and the like may be disposed within the library housing relies, at least in part, on the ability of the picker mechanism of the storage library to maneuver and access the storage slots, media drives, and the like. Typically, the gripper or hand is mounted on a sled or stage which moves along the track. In some examples, the sled rotates to negotiate and move through one or more corner or curved portions of the track as described, e.g., in U.S. Patent Publication No. 2002/014,9870. In other examples, the track itself may rotate to move the sled along different directions as described, e.g., in U.S. Pat. No. 6,496,325. During rotation of the sled and/or track in the corner portions, however, the gripper mechanism generally cannot access storage slots, media drives, and the like, resulting in a loss of usable space (“dead space”) within the library housing.
Additionally, conventional sleds are translated along a track with one or more motors. Generally, the motor is mounted with the sled resulting in a significant amount of vertical space occupied by the transport mechanism and added weight to the sled. Further, in some examples, multiple motors are used, e.g., a separate motor for moving the sled along each axis.
Accordingly, conventional transport systems and methods for controlling a gripper mechanism often have a significant turning radius, significant vertical real estate to provide a driving source that moves with the sled, and/or multiple motors (one for each axis). Any of these features may lead to losses in storage capacity for a given storage library size. For example, a large turning radius effectively eliminates useful service locations that could have existed within the radius. Excessive vertical real estate for a drive source generally compromises the ability to achieve high tape densities as well as force/speed margins because of efforts to keep the mechanism height to a minimum. Additionally, multiple motors to move the gripper mechanism may increase the cost and complexity of the system.